Field of the Invention
The present invention relates to a method for manufacturing an electronic device including a multilayer insulator film.
Description of the Related Art
An electronic device such as a semiconductor device includes a multilayer insulator film including a plurality of insulator layers made of different materials. For forming a hole in the insulator film, the insulator layers made of different materials are etched. The hole may be intended to form an optical waveguide or an electroconductive member therein.
Japanese Patent Laid-Open No. 2012-164942 teaches that openings are formed in a silicon oxide layer and a silicon nitride layer under a condition of low selectivity or a small ratio of the etching rates of silicon oxide and silicon nitride. More specifically, this patent document discloses an anisotropic plasma etching using a mixed gas of a hydrogen-containing fluorocarbon such as CHF3 and any other fluorocarbon gas such as C4F8, oxygen, and an inert gas such as argon.
Japanese Patent Laid-Open No. 2009-272568 discloses a process for etching, for example, silicon oxide and silicon nitride or silicon carbide while the conditions are changed according to the materials.
If a member is embedded in a hole formed in an insulator film, it is desirable that the side wall of the hole has a smooth surface from the viewpoint of reducing the formation of voids.
When etching is performed under a condition of a low selectivity as disclosed in Japanese Patent Laid-Open No. 2012-164942, unfortunately, a smooth side wall cannot be formed in some combinations of the materials of the insulator layers. In addition, the side wall cannot be made smooth by simply changing the etching conditions according to the materials of the layers as disclosed in Japanese Patent Laid-Open No. 2009-272568.